3GPP (3rd Generation Partnership Project) LTE-Advanced (Long Term Evolution Advanced) Study Item considers deploying relay node (hereafter referred to as RN) in a cellular network. One of the main objectives for deploying RNs is to enhance coverage area of a base station by improving throughput of a mobile station (user terminal) that locates in a coverage hole or far from the base station resulting in low signal quality. Hereafter, a base station is referred to as BS or eNB (evolved Node B) and a mobile station or user terminal is referred to as UE (user equipment).
In the radio communication network with relay nodes, an eNB that can provide connection to at least one RN is called Donor eNB, which is hereafter called DeNB. In this specification, in order to distinguish a normal eNB from DeNB, the term DeNB is only used when refers to the eNB that is currently having connection with the RN.
Moreover, in this specification, the term “eNB-UE” is used for referring to UE that establishes a connection with DeNB and the term “RN-UE” is used for referring to UE that establishes a connection with RN. On the other hand, the term “UE” is used when refers to both eNB-UE and RN-UE commonly.
The radio interface that provides radio protocol Layer-1 (Physical Layer) to Layer-3 (RRC (Radio Resource Control) Layer) connection between the DeNB and the RN is referred to as backhaul link or Un interface in this specification. On the other hand, the radio interface that provide radio protocol Layer-1 to Layer-3 connection between DeNB and eNB-UE is referred to as eNB-access link and the radio interface that provide radio protocol Layer-1 to Layer-3 connection between RN and RN-UE is referred to as RN-access link or Uu interface. Currently, 3GPP RAN Working Groups (RAN WGs) are mainly considering a relay system called Type 1 Relay that shares radio resources between the backhaul and eNB-access links (see NPL 1 and NPL 2). There have been proposed several methods for scheduling radio resources in such a relay system. Conventional examples are as follows.
PTL 1 discloses a radio cellular network in which a BS (corresponding to DeNB) receives reports of link qualities of BS-SS (corresponding to eNB-access link) and BS-RS (corresponding to backhaul link) from the eNB-UE and the RN, respectively. Based on these link qualities, the DeNB allocates radio resources to the eNB-UE and the RN.
PTL 2 discloses a radio telecommunication system in which a RN performs periodically a local fair scheduling procedure in order to achieve a fair distribution of available radio resources of the RN, which is represented by a local fairness parameter, and transmits the local fairness parameter to a DeNB. Using the local fairness parameter received from the RN, the DeNB performs a global fair scheduling procedure for determining a fair distribution of available radio resources of the DeNB.
{NFL 1} 3GPP TR 36.912 v9.1.0 (2009-12), “Feasibility study for Further Advancements for E-UTRA (LTE-Advanced)”
{NFL 2} 3GPP TR 36.814 v9.0.0 (2010-03), “Further Advancements for E-UTRA physical layer aspects”
{PTL 1} WO2008/127814A1
{PTL 2} EP2066084A1